The NK-drived exosomes enhance NK cell-based therapy to melanoma cancer

Objectives Exosomes are nanovesicles released by normal and tumor cells, which are detectable in cell culture supernatant and human biological fluids, such as plasma. Functions of exosomes released by “normal” cells are not well understood. In fact, several studies have been carried out on exosomes derived from hematopoietic cells, but very little is known about NK cell exosomes, despite the importance of these cells in innate and adaptive immunity. The aim of the study was to explore effect of NK-derived exosomes on characteristics of NK cells (a-NK) including cytotoxicity to human melanoma cancer (B16F10).

Methods NK92-MI and B16F10 cells were retrovirally transducted to express enhanced firefly luciferase (effluc) gene (B16F10/F and NK/F). Expression of effluc and NK cell surface markers were assessed by using flow cytometry, RT-PCR, western blotting and luciferase activity. After treatment of NK cells with the exosomes derived from the NK cell(NK-Exo). Proliferation rate of NK cells was measured and the cytotoxic effect of NK to B16F10/F cells was also assessed using bioluminescence imaging (BLI). The NKF cells were analyzed in the nude mice with B16F10 xenograft.

Results B16F10 cells were established by co-transfection with both effluc and Thy1.1 genes and selected the Thy 1.1 positive cells by using microbeads. Effluc and the activity of the NKF and B16F10/F cells were confirmed. NK-Exo expressed typical NK markers (CD56 CD16 and CD4) and exerted antitumor to B16F10. NK-Exo increased the proliferation rate of NK cells (p<0.05) and also enhanced the cytotoxic of NK cells to the B16F10/F cells (p<0.001).

Conclusions The results of present study suggest that NK cell treated with NK-Exo has higher therapeutic effect than naive NK cells to the human melanoma cancer, and pretreatment of NK cells with NK-Exo may be useful for the NK cell-based therapeutic approach.